Mirrors That Detect Ripples in Space-Time Were Frozen to Near Absolute Zero - Gizmodo

A team of physicists say they’ve managed to nearly freeze the motion of atoms across four suspended mirrors.

The setting for this experiment was LIGO, the Laser Interferometer Gravitational-Wave Observatory, where physicists look for ripples in space-time created by the collisions of massive objects like black holes.

The observatory relies on four carefully suspended mirrors and laser beams to detect passing gravitational waves, which shift the mirrors ever so slightly, causing the laser beams to briefly wobble. The researchers behind the current experiment took advantage of a break period at LIGO last September to attempt something that had never been done before: cool a human-scale object so much that quantum observations could be made on it.

You can cool an object by sticking it in a freezer, but when you’re a physicist, you can also cool an object by reducing its motion.

“We could actually use the same capability of LIGO to do this other thing, which is to use LIGO to measure the random jiggling motion of these mirrors—use that information which we have about the motion—and apply a counteracting force, so that you know you would stop the atoms from moving,” said Vivishek Sudhir, a quantum physicist at the Massachusetts Institute of Technology and a co-author of the paper, in a video call.

But to behave like a quantum system, the team also needed to remove the noise caused by heat.

Gravity acts more intensely on massive objects, so having such a large object to work with is a big step toward exploring how the force may or may not engage with the quantum world.